Optical scanning apparatus

ABSTRACT

An optical system is disclosed herein for scanning a stationary original and placing a flowing light image thereof upon a moving light receiving member. The original is placed upon a light transmitting platen and successive incremental areas thereon scanned by means of a moving lamp and a moving lens which cooperate to focus a flowing image of the original on the moving surface in synchronous timed relation therewith. A shutter is positioned adjacent to the optical path and is arranged to move into a light blocking position to prevent exposure of the photosensitive surface when said surface is not in motion.

United States Patent [191 Schaeffer et al.

OPTICAL SCANNING APPARATUS Inventors: Robert A. Schaeffer; William T.

White, both of Rochester; Samuel D. Coriale, Webster, all of NY.

Assignee: Xerox Corporation, Rochester, N.Y.

Filed:

Appl. No.: 174,946

Aug. 25, 1971 Related US. Application Data Division of Ser. No. 859,929,Sept. 22, 1969.

US. Cl 355/18, 355/8, 355/25,

Int. Cl. G03b 27/16 Field of Search 355/8, 47, 82, 64,

References Cited UNITED STATES PATENTS I 5/1970 Wirley 355/8 X Nov. 27,1973 2,357,827 9/1944 Hopkins ..355/47 3,092,004 6/1963 Lewis ..355/82Primary Examiner-John M. Horan Attorney-Paul M. Enlow et al.

[. ABSTRACT An optical system is disclosed herein for scanning astationary original and placing a flowing light image thereof upon amoving light receiving member. The

original is placedupon a light transmitting platen and successiveincremental areas thereon scanned by means of a moving lamp and a movinglens which cooperate to focus aflowing image of the original on themoving surface in synchronous timed relation therewith. A shutter ispositioned adjacent to the optical path and is arranged to move into alight blocking position-to prevent exposure of the photosensitivesurface when said surface is not in motion.

3 Claims, 12 Drawing Figures PATENTED NOV 27 I975 SHEET u 0F 8 "has iPAIENTEDNUVZY I915 SHEET 8 [IF 8 FIG. /2

Mn. v

OPTICAL SCANNING APPARATUS This is adivision of application, Ser. N...859,929

filed Sept. 22, 1969. I I

This invention relates to an optical scanning system and, in particular,toapparatus for placing a flowing light image of a stationary originalupon a moving photosensitive surface.

It has always been desirous in automatic xerographic reproducingmachines to hold the original object to be a plane. The stationaryplaten also affords a wide freedom of control over the composition ofthe original wherein subjectfrnatter from many different sources can beformulated into a single composite which is then easily reproduced. I

These many advantages associated with the flat support platen, however,were never fully realized lintil Mayo, in U.S. Pat. No. 3,062,094,disclosed a moving scanning apparatus by which a flowing light imagecould be placed in synchronous timed relation with a moving lightreceiving surface to produce a nondistorted image of the original. Sincethe Mayo invention, the copying art, and in particular the xerographicart, has made many sigificant advances in process and materials. Highspeed, sensitive, photoreceptors are now available making it possible toreproduce images of originals during extremely short exposure'periods.Although the Mayo device has met with wide commerical success, itnevertheless has been found to have certain limitations when used inhighspeed machines of this type.

It is therefore an object of this invention to improve optical scanningapparatus for placing a flowing light image of a stationary originalupon a moving photosensitive member. i

A further object of this invention is to improve xerographic scanningapparatus by preventing ambient light from passing through the scanningsystem and overexposing the photoconductive member during periods whenthe photoconductive member is not in use.

A still further object of this invention is to provide an opticalscanning system for placing a flowing light image of a stationaryoriginal on a moving photosensitive surface for use in high speedautomatic xerographic reproducing apparatus.

A still further object of this invention is to improve automaticxerography by reducing the amount of wasted machine time between copyingcycles.

Yet another object of this invention is to provide a moving scanningapparatus in which the scanning mechanism is returned at a more rapidrate than the scanning rate reciprocating cycle of the elements.

These and other objects of the present invention are attained by meansof a scanning system having a stationary platen for supporting anoriginal to be copied, a source of illumination relation in a movablecarriage and being arranged to illuminate incremental bands upon anoriginal supported upon the platen, a moving light receiving memberpositioned to receive reflected light images from an original on theplaten surface, a

2 movable lens interposed between the moving light reciving member andthe source of illumination for focusing illuminated areas on thecopyboard onto the reciving member, means to drive the lens and the lampcarriage along their respective individual paths of travel atpredetermined rates in relation to the light receiving surface wherein aflowing ligh t'image is placed on the moving surface, means toreturn thelens and lamp carriageto their respective starting position at a rate inexcess of the predetermined scanning rate, and

light blocking means positioned adjacent to the'optical path and beingarranged to move into light blocking relation therewith when the lightreceiving member is not in motion. I

For a better understanding of the invention as well as other objects andfeatures thereof, reference is had to the following detailed descriptionof the invention to be read in connection with the accompanyingdrawings, wherein:

FIG. 1 is a schematic side elevation of an automatic xerographic machineutilizing the present apparatus;

FIG. 2 is a partial side elevation in section showing the opticalscanning mechanism of the instant invention; I

FIG. 3 is a partial side elevation with portions broken away showing thelens drive mechanism ofthe'pre sent apparatus; i v W FIG. 4 is a partialside elevationiillustrating the shutter slide and the control mechanismassociated therewith;

FIG. 5 is a partial section takerialong lines 5-5 in FIG. 4 showing theexposure slit and associated shutter mechanism of the present invention;

.lens carriage of the present invention;

FIG. 9 is a partial front elevation in section of the shutterillustrated in FIG. 7; Z

FIG. 10 is a side elevation of a alternate embodiment of the lampcarriage shown iii FIG. 2;

FIG. 11 is a partial view in section illustrating mechanism to supportthe image mirrors shown in FIG. 2; and

FIG. 12 is a'partial section taken along lines 12-12 in FIG. 6 showingthe lamp drive mechanism.

As illustrated in FIG. 1, the apparatus of the present invention isshown herein embodied in an automatic xerographic reproducing machinecapable of producing both simplexed or duplexed copy. Although theapparatus of the present invention is particularly well adapted for usein automatic xerographic machines, it should become evident from thediscussion below that it is equally well adapted for use in a widevariety of ap-' paratus and is not necessarily limited in itsapplication series of xerographic processing stations. The drum surfaceand the other machine operating'mechanisms are driven at a predeterminedspeed relative to each other from a single drive system (not shown) andthe operations coordinated in order to produce proper cooperation of thevarious processing stations.

An original, such as a document, book, or the like, is placed upon atransparent platen 14 and the original scanned by a moving opticalscanning system to produce a flowing light image thereof. Fundamentally,the scanning system includes a single aperture lamp 15 and a lenselement 18 arranged to move in individual paths to transverse the planeof the platen. As will be explained below, the scanning rates of thelamp and lens are controlled wherein a flowing light image is placed inan undistortedmanner upon the moving drum surface. The optical path ofthe system is folded by means of a pair of image mirrors l9 and 20 sothat the light image is placed on the bottom of the drum surface atexposure station B. Prior to the imaging of the drum surface, however,the photoconductive drum surface is uniformly charged by means of acorotron 13 positioned in charging station A. Under the influence of theflowing light image, the uniform charge is selectively discharged in thenon-imaged areas whereby a latent electrostatic image of the original isproduced on the drum surface.

The latent image is next transported on the drum through a developerhousing 22 located in a developing station C where the charged drumsurface is treated with a developer material 21 possessing charged tonerparticles having a polarity opposite to that of the latent electrostaticimage. A supply of developer material is supported in the bottom of thedeveloper housing and is delivered to an elevated entrance to thedevelopment zone by means of a bucket conveyor system 23. The developermaterial 21 is caused to flow downwardly in contact with the upwardlymoving drum surface under controlled conditions wherein charged tonerparticles are attracted into the image areas thus making the imagevisible.

The moving drum surface next transports the developed image to atransfer station D where a cut sheet of final support material, as forexample, paper, is moved from either upper supply tray 52 or lowersupply tray 53 through the sheet registration mechanism 24 intocoordinated synchronous moving contact with the image on the. drumsurface. The backside of the copy sheet is sprayed with an ion dischargefrom a tranfer corotron 24 inducing a charge thereon of a polarity andmagnitude sufficient to attract the toner material from the drum surfaceto the final support material. The sheet is then stripped from the drumsurface by means of stripper finger 28 and directed into contact with astationary vacuum sheet transport 29.

Although a preponderance of the toner material is transferred to thecopy sheet, invariably some residual toner is left behind on the drumsurface after image transfer. This residual toner is removed from thedrum as it moves through cleaning station E. Here the residual toner isfirst brought under the influence of a cleaning corotron 30 adapted toneutralize the electrostatic charge remaining on the toner material. Theneutralized toner is then mechanically cleaned from the drum surface andcollected within a housing 31. A conveyor system, moving through anendless path through guide tubes 32, transports the collected residualtoner back into the developing station where it can be once again usedin the xerographic developing process.

Simultaneously, with the cleaning operation, the image bearing supportmaterial is moved along sheet transport 29 into a fusing station F wherethe sheet passes between upper fuser roll 34 and lower roll 35 making upfuser assembly 33. The two rolls are mounted in operative relation sothat the roll coact to support a sheet of material in pressure drivingcontact therebetween. The outer surface of the lower roll is heated bymeans of a horizontally arranged elongated radiant heat source 38 thatis positioned in close proximity to the roll surface adjacent to thepoint at which the roll contacts the image bearing support material. Asthe heated roll is rotated in the direction indicated, the hot rollsurface is pressed into intimate contact with the image bearingmaterial. Sufficient mechanical and heat energy is rapidly transferredin the contact zone to the sheet to fuse the toner particles to thefinal support material.

The now fixed copy sheet is passed through a curvalinear sheet guide 39into cooperating advancing rolls 40, 41 which cooperate to forward thesheet through a linear sheet guide 42. A second pair of advancing rolls43, 44 further forward the sheet into a movable sheet guide systemgenerally referenced 45. As shown in FIG. 1, the movable sheet guidesystem 45 and its associated advancing rolls 48, 49 are pivotallymounted about shaft 50; the guide being positonable to direct a copysheet into either catch tray 51 or upper supply tray 52. A mode ofoperation is provided, by which a simplexed copy sheet can be stored inthe upper supply tray and refed through the xerographic processingstations to place a second image on the opposite side thereof.

It is believed that the foregoing description is sufficient for purposesof the present application to show the general operation of axerographic reproducing machine embodying the teachings of the presentinvention.

Referring now to the specific subject matter of the present invention,illustrated in FIG. 2-12 the preferred embodiment of the exposuremechanism of this apparatus is designed to use a moving optical scanningor projection assembly to scan the object to be reproduced and toproject a flowing light image thereof onto the surface of the rotatinglight sensitive drum. The length of scan and the projection of the imageof the object onto the surface of the drum is timed relation with themovement of the drum is controlled by the scan mechanism which will beexplained in greater detail below. The optical scanning of the object,which is placed upon the fixed platen 14, is accomplished by means of amovable lens system. The lens element is arranged to move in a pathtransverse to the plane of the platen in predetermined timed relationwith the drum surface to scan an original supported thereon. Althoughany suitable source of illumination can be employed to illuminate theoriginal on the platen, in this preferred embodiment of the inventionthere is provided a lamp carriage supporting a single elongated glowdischarge tube being capable of projecting an incremental band ofillumination forward of said carriage in the direction of scan. The lampis also arranged to move in a path transverse to the platen in timedrelation with the moving photosensitive plate. The moving lamp bandsprojects successive bands of illumination which results in a uniformillumination of the object supported thereon.

A pair of fixed image mirrors mounted below the lens and the drumsurface reflect the light image transmitted by the lens through anaperture slit 111 positioned adjacent to the drum onto the bottomsurface of said drum. 6

In order to conserve valuable machine time in a high speed automaticreproducing machine of the type herein disclosed, it is essentialthatthe time to restore both the lamp and the lens elements to theirrespective a light image of a stationary original onto the movingphotosensitive surface of rotating drum vI linclude side plates 55 and56 which may be formed integrally with the main machine frame or,optionally, as illustrated in FIGS. 2 and 6, as separate plates boltedor otherwise secured to the main frame of the machine. The two sideplates are connected together in fixed parallel relation to each otherand support therebetween the lamp carriage drive shaft 58 and the lampcarriage support rod 59.

Stationary platen 14 is mounted in a suitable receiving opening in thetop cover plate 60 of the machine as illustrated in FlG. 2. Thecopyboard consists of a light transmitting surface 61, usuallyconstructed of optically clear glass, which is supported upon a mountingframe 62 and the frame-secured to underside of the top cover plate. Theplaten is securely supported on three sides in the frame while theremaining side, that is, the left-hand side as shown in FIG. 2, heldsuspended at the edge of the main machine frame. An inclined member 63,which is affixed to left-handside, plate 55, is held in abutment withthe suspended edge of the platen andtherewith to provide a continuousangulated surface upon which a bound original, such as a book, magazine,or the like, may be conveniently supported in a nondamaging postureduring exposure. A book 68 illustrated by dotted lines, is shownsupported on the platen in FIG. 2. Althoughnot shown, a suitable platencover capable of both protecting the top surface of the platen andholding an original in intimate contact therewith, is hinged upon oneedge of frame 62.

In a high speed xerographic reproducing apparatus as herein disclosed, ahighly sensitive photoconductive plate, that is, a plate which isextremely fast in both a photographic and a xerographic sense, isrequired in order to completely expose the plate during the relativelyshort exposure period. Because of the plate sensitivity, an illuminationsource of relatively low intensity can be employed in the presentapparatus. For this purpose, there is provided a lamp carriage 71inovably supported between the lamp carriage drive shaft 58 and the lampcarriage support rod 59 and being arranged to reciprocally drive anelongated light source 15 along a path of travel transverse to theplaten.

As illustrated in FIG. 2, 6 and 12, the lamp carriage 71 issubstantially L-Shaped along the major portion of its length and has apair of electrical adapters 70 mounted in vertical parallel relationshipat opposite ends of the carriage capable of supporting a source ofillumination therebetween. In the preferred embodiment, the lampadapters are arranged to support a single, elongated tubularfluorescent-type lamp beneath the support platen with the axialcenterline of the lamp in parallel relation with the platen surface. Theouter surface of the lamp is generally opaque with a light transmitting.slit aperture 72 formed therein which extends longitudinally across thesurface of the lamp. To energize the lamp, the lamp adapters areelectrically connected to a suitable source of energy (not shown) bymeans of a flexible cable.

Often times itwill be physically impossible to position the illuminationsource in close proximity to the platen surface in the manner disclosedin this preferred embodiment of the present invention. It is well knownthat the intensity of illumination drops off rapdily the further thesource is moved from the irradiated body. It is therefore quite feasiblethat more than one illumination source will be needed to produce therequired illumination at the platen surface. An alternate embodiment ofthe lamp carriage is shown in FIG. 10 in which two vertically alignedlamps 15 similar. to the lamp herein disclosed are supported in the lampcarriage 69. The elongated slit apertures 72 associated with the lampsare arranged to focus upon a single incremental area on the platen, thearea being forward of the lamp carriage in the direction of scan. As canbe seen, by mounting the lamps in this manner, a wide flexibilityandplacement of the lamp carriage is afforded without departing from theteachings of the present invention.

A switching arrangement is provided to control the energy source whereinthe lamp is energized at the start of a scanning portion of the copyingcycle and held energized for a period of time sufficient to allow thelamp to sweep acrossthe entire surface of the platen. However, as thecarriage returns to the start of scan position, the power to the lamp isreduced to a level below the threshold potential of the lamp to hold thelamp inactive during the return pass. A pair of limit switches 73 and 74are affixed to the machine frame with their respective actuating armspositioned in interferring relationship with a portion of the lampcarriage. As the clamp carriage starts forward in the direction of scan,the contact of limit switch 73 is closed allowing current to flow fromthe electrical source to the lamp. Upon completion of the pass, thecontact of limit switch 74 is made sending a signal to the energy sourcereducing the available potential at the lamp to just below threshold. Inthis manner, the amount of illumination passed through the opticalsystem on to the sensitive plate is minimized to prevent overexposure ofthe drum.

As illustrated in FIG. 2, the elongated light transmitting aperture 72in the lamp is positioned to project a band of illumination well forwardof the lamp carriage in the direction of scan. As the lamp is moved fromleft to right as shown in FIG. 6. the band of illumination moves acrossthe platen into the corner fonned by the unsupported edge of the platenand the inclined machine member 63. As can be seen, the presentarrangement gives the scanning apparatus the ability to look intocorners or otherwise inaccessible areas.

A dependent bearing housing 76 is provided at the right-hand end of thelamp carriage in which is mounted in a journal bearing 77 (FIG. 12) andthe bearing arranged to ride upon the rotatably supported drive shaft68. A pin 78 passes through both the housing and the bearing in anopening provided and rides freely in a helix groove 79 formed in theshaft. The shaft extends through plate 56 and is operatively connectedby means of a pair-of spiral bevel gears 84 and 85 to drive sprocket 82locked to the main drive system. In this manner, the movement of thelamp carriage is coordinated in timed relation with the movement of thedrum surface and the lens element.

Another dependent bearing housing 80 is formed in the opposite end ofthe lamp carriage having an internal bearing surface adapted to rideupon support rod 59. Both the rod and bearing surface are constructed ofa plastic material, such as nylon, polyethylene, teraphthalate .ortetrafluorethylene having a low coefficient of friction and whichexhibits good tensil strength and wear properties at room temperature.The drive shaft is also constructed of a similar material to facilita tethe free movement of the carriage back and forth along its predeterminedpath of travel.

As the drive rod is rotated in the manner described above, the helixgroove therein acts against stationarily held pin 78 driving the lampcarriage'along its path of travel, below the platen. The helix groove 79is, in effect, a cylindrical cam which imparts a prescribed motion tothe lamp carriage. At the start of a scanning cycle, the cam causes thecarriage to first rapidly accelerate to the scanning velocity. A linearmotion is then translated to the carriage driving the lamp across theplaten at a uniform rate during the scanning pass. At the end of thescanning pass, the carriage is rapidly decelerated to a zero velocityand the direction of travel reversed. A rapid but harmonic return motionis imparted from the cylindrical cam to the carriage causing thecarriage to rapidly accelerate and then decelerate to a zero velocity.during the return phase of thecopying cycle. To minimize wasted machinetime between scanning passes, the carriage is restored to the start ofscan position, a distance of approximately 10 inches, in about 8.5seconds.

The forces generated during these extremely short 7 system which aretransmitted by the drive shaft to the machine frame where they arereadily absorbed.

Because of the novel lamp support and drive arrangement hereindisclosed, the lamp carriage is capable of being positively driventhrough both the scanning phase and the return phase of each copyingcycle which permits the lamp'carriage to be accelerated and deceleratedat rates heretofore unobtainable in this type of scanning apparatus.

Positioned directly below the platen in position to receive a reflectedlight image of an object or original supported thereon is an opticalsupport generally referred to as 100. The optical system is basicallymade up of a lens element 18 positioned in a lens carriage 103 and twoimage mirrors 19 and 20, all of which are supported within a casting104. The casting is supported by precision surfaces arranged to rest ontwo horizontal precision tie bars and 91 to accurately seat the castingin a predetermined position within the main machine frame.

The lower edge of each image mirror is carried in a flexible channel 96(FIG. 11), constructed of an elastomeric or felt material, and themirrors adjustably supported within the casting at three individualpoints by means of clip assemblies generally referred to as 93. Asillustrated in FIG. 5 and 11, each clip assembly comprises an eccentriccam 94 which is rotatably mounted on a stub shaft 95 anchored in thecasting. A spring member 97 is operatively connected at one end to theeccentric cam while the opposite end of the spring is biased intosupporting contact with the bottom surface of the reflecting surfacefByrotating the cams, the angular position of the individual mirrors inreference to the optical path of the system can be adjusted wherein alight image projected by the system passes through the exposure slitonto the rotating drum surface Lens element 18 is slidably supportedbetween two parallel horizontal rails and 106 which are anchored in thetop part of the optical support casting adjacent to the image receivingopening therein. The lens is mounted in a lens carriage 103 and thecarriage, in turn, supported upon the rails in journal bearings providedwherein the carriage moves freely in a plane substahtially parallel tothe plane of the exposure platen 61. As shown in FIG. 8, one side of thelens carriage is supported upon an eccentric bearing 108 and theeccentric bearing locked to an adjusting arm 109. The adjusting arm isprovided with a slotted hole 113. A stud 1 14 passes through the slottedhole and is threaded into the main portion of the lens carriage housingthus providing a means to lock the eccentric bearing in a predeterminedposition. A slighthorizontal adjustment of the lens isafforded byloosening stud 111 and turning the adjustable arm in the desireddirection. A further adjustment of the lens element is provided byeccentric bearing 108. Rotation of the bearing causes .the carriage toswing'about rail 106 to reposition the optical centerline of the systemtransversely in reference to the drum surface. By raising or loweringthe lens element, the lens can be squared to the object and image planesto obtain optimum image quality.

As illustrated in FIG. 2, the top of the optical support casting isprovided with a cap 97 enclosing most of the top opening to the opticalcasting. The cap has an image receiving aperture 98 therein carrying abellowstype movable light shield 99. An opening in the movable shield isprovided through which the lens element passes in lighttightrelationship therewith. The remaining portion of the casting isalso made light-tight wherein the only light passing interior thecasting in the light transmitted by the lens element. In this manner,the sensitive photoconductive surface is protected from beingoverexposed by ambient light which otherwise might inadvertently enterthe system.

At the light exit opening in the optical casting, which is adjacent tothe lower drum surface, there is affixed a slotted light shield 110having an'elongated slit or aperture 111 therein arranged to extendtransversely across the bottom portion of the drum surface. The shieldfunctions as a field stop to limit the image field striking the drumsurface.

Because the photoconductive surface of the Xerographic drum is curved,and the drum is in constant motion while the machine is in operation,the image of an original cannot be projected in its entirety directlyonto the photoconductive surface. In order to obtain, a clear, welldefined, image on'the drum surface, the lens element is moved toprojectcontinu'ous images of incremental areas of'the copy onto themoving drum surface as it scans across the-platen. The movement of thelens is;-synchronized with the movement-f the drumthrough the drivesystem so that the incremental areas are properly registeredsuccessively with each other through the field stop onto the drum to atrue reproduction of the copy.

To effect uniform illumination of the copy, the light source is moveduniformly across the original as previously described and the motion ofthe light source coordinatd with the movement of the lens and themovement of the drum surface. This synchornization and coordination ofmovement of the lens in correlation with the light source and the movingdrum surface is obtained by means of a lens control systemcomprising adrive cam and linkage assembly is drivenby a drive mechanism locked tothe drum shaft 12.Referring now to FIG. 3, a twolobe cam 120 and theassociated drive mechanism is driven'from shaft 12 and the assemblymounted in the machine frame upon the drum support casting lZl. A camfollower arm 122 is pivotally mounted in the'drum casting about a pivotpin 123. The follower arm is operatively connected to one endof rockerarm 125 by means of an adjusting screw ,124 and the. rockerarm'rotatably mounted in the rocker arm support casting 127 mounted tothe lower portion of the optical support casting 'on a shaft 129. Theopposite end of the rocker arm is movably connected to the lamp carriageby means of a link 130. In operation, the cam follower l32'is'b iasedinto contact with the working surface of the cam by the force exerted onthe rocker arm by spring 126 so that the entire prescribed motion of thecamis imparted throughthe associated mechanism, to the lens carriage.The face of each cam lobe is generated so the individual lobes translatea motion to the lens carriage producinga linear scan across the platenand a rapid return to the start of scan position. r a

The present apparatus is designed to make two copies for each revolutionof the drum surface. The cam must therefore reciprocate the lenscarriage through two copy cycles for each revolution'of the drumsurface. However, it shouldbe clear that the present apparatus isperfectly well suited to image the drum surface any number of times perdrum revolution and the presentapparatus is not limited to thisparticular two lobe cam arrangement. ltshould be noted that the lenscontrol cam controlsthemotionofthe lens through both the scan and returnof scan passes.

It should be noted that-the optical apparatus of the type hereindisclosed may be used for the reproduction of the same size'of copyorfor larger or smallerrepro-, ductions. When aone to one reproductionis to be made, the lens is positioned optically equally distant fromboth the copy and the moving surface'of the photoconductive drum. When'asmaller or reduced size reproduction is desired, the lens must bepositioned optically closer to the xerographic drum than tothe copy, andobviously, the opposite arrangement" must be made when largerreproductions are" desired. In this embodi- 10 ment disclosed,*with't'he lens positioned mid-point in theopticalpath between the copyand the xerographic dru, thelens mii'st i'nove through a distance atleast one half the length of the copy at a speed equal to one half thelinear speed of the surface of the dru, while the light source, whichtranverses at least the length of the copy is moved at thesameli'near-speed as that of the drum and are coordinated wherein therespective elements starforward in unison at'the beginning of eachscanning pass.

The optical scanning system of the present apparatus,

because it is locked to the drum shaft, will be in motion only when thedrum surface; is moving. In operation, the machine logic will holdzthexerographic processing stations in a standby condition when the machineis on. After placing a copy on the copyboard, the desired number ofcopies is set into the machine select counter and the copy buttondepressed. Atthis time, the drum begins to rotate and continues torotate until the required number of scanning cycles completed. When theselectcounter reaches coincidence, the machine returns to a standbycondition and the drum and optical scanning systems are idled. It isquite conceivable that when thedrum is held immobile in one position fora long'period of time, the surface of the drumadjacent to the field stopwill be continually exposed to ambient light passing through the opticalsystemwhen the platen cover is in a raised position. As previously no-.ted,prolonged exposure of the drum surface to illumination canseriously effect the drum s photoconductive properties. The highlysensitive drum surfaces will become fatigued after a period of timeresulting in a nonuniformity in the quality of copy being produced. An

automatic shutter, generally referred to as 140, is providedinthepresent apparatus which moves into lighttight relation with thelight shield to close the field stop opening when the drum surface isnot in motion. The shutter basically comprises a substantially flatrigid plate 141 having upwardly rolled edges 142 which ride gage a pairof segmented pinions 151. A shaft 152 is rotatably carried in thevertical support members in bearing blocks 155 provided.v The shaft,securely sup- :ports the segemented pinions in spaced relation thereonin a position to operatively engage the racks on fithe underside of theshutter. The shaft extends beyond the righthand vertical support memberas shown in FIG. 9 and has a crank arm 156 secured at the extreme endthereof. v

A drive motor MOT-l, mounted in the side of the optical support casting104 is operatively connected to 'theshutter-crank arm by means of a-pairof lins 157 and 158; As the motor shaft rotates through the shutter iscaused to move laterally into light sealing relation with the shield toclose the field stop opening. Further rotation of the motor throughanother 18020 1 causes the connecting linkageto pull the shutter back asilluss trated in FIG. 4 to allow light to pass through the field stoponto the drum surface. An actuator arm 159 is also mounted upon themotor shaft and is arranged to hold contact 160 is electricallyconnected to control unit 161 (FIG. 4) in the machinelogic system. Whenthe select counter in the logic system reaches coincidence and the drumstops rotating, an electrical signal is sent to the control unit 161which activates the motor MOT- 1. The motor will continue to rotate inthe direction indicated until a change in the condition of the contact160 is sensed. As can be seen the condition of the contact changes every180 of shaft rotation so that the shuter is housed in an open or closedrelationship with the field stop. That is, once a change of conditionsignal is received, the shutter will either be moved by the motor to theopposite condition.

While this invention has been described with reference to the structuredisclosed herein, it is not confined to the details set forth, and thisapplication is intended to cover such modifications or changes as maycome within the scope of the following claims.

What is claimed is:

1. An apparatus for projecting a flowing light image onto a moving lightreceiving surface of the type wherein a lens element is arranged tofocus light re-' supporting the original, said platen memberhaving oneside edge thereof unsupported by said frame member and suspendedthereover;

an elongated lamp positioned adjacent said platen member with thelongitudinal axis of said lamp being substantially parallel to saidplaten member, said lamp being substantiallyopaque and having a lightransmitting portion extending lingitudinally across the surface thereof,said lamp being arranged so that the light transmitting portion directsan incremental band of illumination forwardo of said lamp in thedirection of the unsupported side edge of said platen member; and

means for moving said lamp in a time relation with the lens to focussuccessive incremental bands of illumination, said moving meansadvancing said lamp in a direction substantially transverse to thelongitudinal axis of said lamp and substantially parallel to said platenmember toward the unsupported side edge of saidplaten member.

, 2. An apparatus as recited in claim 1, wherein said movingmeansincludes a rotary driven, substantially cylindrical cam member arrangedto advance said lamp and lens element during the scanning pass and toreturn said lamp and lens element to respective start of scan positionsafter each scanning pass at a rate in excess of the advancing rate.

3. An apparatus as recited in claim 2, further includfirst switch'meansaffixed to said frame member and arranged to energize said lamp memberat the satart of the scanning pass; and second switch means affixed tosaid frame member and arranged to de-energize said lamp member at theend of the scanning pass, said lamp being deenergized during the returnto the start of scan position.

1. An apparatus for projecting a flowing light image onto a moving lightreceiving surface of the type wherein a lens element is arranged tofocus light reflected from an original through a slit aperture onto thelight receiving surface, the lens element scans the original at a raterelative to the light receiving surface to place a flowing light imageof the stationary original thereon, wherein the improvement includes: aframemember; a platen member mounted on said frame member for supportingthe original, said platen member having one side edge thereofunsupported by said frame member and suspended thereover; an elongatedlamp positioned adjacent said platen member with the longitudinal axisof said lamp being substantially parallel to said platen member, saidlamp being substantially opaque and having a light ransmitting portionextending lingitudinally across the surface thereof, said lamp beingarranged so that the light transmitting portion directs an incrementalband of illumination forwardo of said lamp in the direction of theunsupported side edge of said platen member; and means for moving saidlamp in a time relation with the lens to focus successive incrementalbands of illumination, said moving means advancing said lamp in adirection substantially transverse to the longitudinal axis of said lampand substantially parallel to said platen member toward the unsupportedside edge of said platen member.
 2. An apparatus as recited in claim 1,wherein said movingmeans includes a rotary driven, substantiallycylindrical cam member arranged to advance said lamp and lens elementduring the scanning pass and to return said lamp and lens element torespective start of scan positions after each scanning pass at a rate inexcess of the advancing rate.
 3. An apparatus as recited in claim 2,further including: first switch means affixed to said frame member andarranged to energize said lamp member at the satart of the scanningpass; and second switch means affixed to said frame member and arrangedto de-energize said lamp member at the end of the scanning pass, saidlamp being de-energized during the return to the start of scan position.